Film

February 28, 2011

The Economist reports on a fascinating study of crowd behaviour in animals, otherwise known as swarming: the way in which groups of animals manage to order themselves in ways that further their survival as a group, even when most or all of them have only an extremely partial view of what's going on. As individuals, ants are pretty stupid, but as a group they find paths to food and build sophisticated structures (although see here for what happens when ants go bad).

Are there leaders in such groups? A professor at Princeton has been modelling the behaviour of shoals of fish, and has found that to a certain extent, yes there are. But the the leadership tasks are passed around with great efficiency and - crucially - there are only a few leaders at any one time:

He posited that how they swim will depend on each individual’s competing tendencies to stick close to the others (and thus move in the same direction as them) while not actually getting too close to any particular other fish. It turns out that by fiddling with these tendencies, a virtual shoal can be made to swirl spontaneously in a circle, just like some real species do.

That is a start. But real shoals do not exist to swim in circles. Their purpose is to help their members eat and avoid being eaten. At any one time, however, only some individuals know about—and can thus react to—food and threats. Dr Couzin therefore wanted to find out how such temporary leaders influence the behaviour of the rest. At any one time, however, only some individuals know about—and can thus react to—food and threats. Dr Couzin therefore wanted to find out how such temporary leaders influence the behaviour of the rest.

He discovered that leadership is extremely efficient. The larger a shoal is, the smaller is the proportion of it that needs to know what is actually going on for it to feed and avoid predation effectively. Indeed, having too many leaders with conflicting opinions results in confusion. At least, that is true in the model. He is now testing it in reality.

The next step is to model the behaviour of humans in crowds. Then, presumably, Congress.